
// Make newform 252.2.j.a in Magma, downloaded from the LMFDB on 23 April 2024.
// To make the character of type GrpDrchElt, type "MakeCharacter_252_j();"
// To make the character of type GrpDrchElt with Codomain the HeckeField, type "MakeCharacter_252_j_Hecke();"
// To make the coeffs of the qexp of the newform in the Hecke field type "qexpCoeffs();"
// To make the newform (type ModFrm), type "MakeNewformModFrm_252_2_j_a();".
// This may take a long time!  To see verbose output, uncomment the SetVerbose lines below.
// The precision argument determines an initial guess on how many Fourier coefficients to use.
// This guess is increased enough to uniquely determine the newform.
// To make the Hecke irreducible modular symbols subspace (type ModSym)
// containing the newform, type "MakeNewformModSym_252_2_j_a();".
// This may take a long time!  To see verbose output, uncomment the SetVerbose line below.
// The default sign is -1.  You can change this with the optional parameter "sign".
function ConvertToHeckeField(input: pass_field := false, Kf := [])
    if not pass_field then
        poly := [3, -12, 19, -15, 10, -3, 1];
        Kf := NumberField(Polynomial([elt : elt in poly]));
        AssignNames(~Kf, ["nu"]);
    end if;
    Rf_num := [[1, 0, 0, 0, 0, 0], [0, 1, 0, 0, 0, 0], [6, 0, 1, 5, -1, 1], [0, -3, 2, -5, 1, -1], [6, -21, 19, -16, 5, -2], [-9, 33, -22, 19, -5, 2]];
    Rf_basisdens := [1, 1, 3, 3, 3, 3];
    Rf_basisnums := ChangeUniverse([[z : z in elt] : elt in Rf_num], Kf);
    Rfbasis := [Rf_basisnums[i]/Rf_basisdens[i] : i in [1..Degree(Kf)]];
    inp_vec := Vector(Rfbasis)*ChangeRing(Transpose(Matrix([[elt : elt in row] : row in input])),Kf);
    return Eltseq(inp_vec);
end function;


// To make the character of type GrpDrchElt, type "MakeCharacter_252_j();"
function MakeCharacter_252_j()
    N := 252;
    order := 3;
    char_gens := [127, 29, 73];
    v := [3, 1, 3];
    // chi(gens[i]) = zeta^v[i]
    assert UnitGenerators(DirichletGroup(N)) eq char_gens;
    F := CyclotomicField(order);
    chi := DirichletCharacterFromValuesOnUnitGenerators(DirichletGroup(N,F),[F|F.1^e:e in v]);
    return MinimalBaseRingCharacter(chi);
end function;

// To make the character of type GrpDrchElt with Codomain the HeckeField, type "MakeCharacter_252_j_Hecke();"
function MakeCharacter_252_j_Hecke(Kf)
    N := 252;
    order := 3;
    char_gens := [127, 29, 73];
    char_values := [[1, 0, 0, 0, 0, 0], [0, 0, 0, 0, 1, 0], [1, 0, 0, 0, 0, 0]];
    assert UnitGenerators(DirichletGroup(N)) eq char_gens;
    values := ConvertToHeckeField(char_values : pass_field := true, Kf := Kf); // the value of chi on the gens as elements in the Hecke field
    F := Universe(values);// the Hecke field
    chi := DirichletCharacterFromValuesOnUnitGenerators(DirichletGroup(N,F),values);
    return chi;
end function;


function ExtendMultiplicatively(weight, aps, character)
    prec := NextPrime(NthPrime(#aps)) - 1; // we will able to figure out a_0 ... a_prec
    primes := PrimesUpTo(prec);
    prime_powers := primes;
    assert #primes eq #aps;
    log_prec := Floor(Log(prec)/Log(2)); // prec < 2^(log_prec+1)
    F := Universe(aps);
    FXY<X, Y> := PolynomialRing(F, 2);
    // 1/(1 - a_p T + p^(weight - 1) * char(p) T^2) = 1 + a_p T + a_{p^2} T^2 + ...
    R<T> := PowerSeriesRing(FXY : Precision := log_prec + 1);
    recursion := Coefficients(1/(1 - X*T + Y*T^2));
    coeffs := [F!0: i in [1..(prec+1)]];
    coeffs[1] := 1; //a_1
    for i := 1 to #primes do
        p := primes[i];
        coeffs[p] := aps[i];
        b := p^(weight - 1) * F!character(p);
        r := 2;
        p_power := p * p;
        //deals with powers of p
        while p_power le prec do
            Append(~prime_powers, p_power);
            coeffs[p_power] := Evaluate(recursion[r + 1], [aps[i], b]);
            p_power *:= p;
            r +:= 1;
        end while;    
    end for;
    Sort(~prime_powers);
    for pp in prime_powers do
        for k := 1 to Floor(prec/pp) do
            if GCD(k, pp) eq 1 then
                coeffs[pp*k] := coeffs[pp]*coeffs[k];
            end if;
        end for;
    end for;
    return coeffs;
end function;


function qexpCoeffs()
    // To make the coeffs of the qexp of the newform in the Hecke field type "qexpCoeffs();"
    weight := 2;
    raw_aps := [[0, 0, 0, 0, 0, 0], [0, 0, 1, 0, 1, 0], [0, -1, 0, 0, 0, 1], [1, 0, 0, 0, 1, 0], [-1, 1, -1, 1, -1, 1], [2, -4, 0, 2, -1, 0], [2, -1, 1, 3, -1, 0], [1, -1, -3, -1, -1, 0], [-1, 0, 0, -1, 5, 2], [-1, -3, -2, -3, -1, 2], [0, 3, 0, 0, 0, -3], [0, -2, -3, 1, -2, 0], [-2, 1, 0, -2, 1, 3], [0, -1, 3, -1, 0, -3], [-8, -2, -3, -2, -8, 3], [1, 1, 0, -2, 1, 0], [1, 0, 0, 1, 10, -2], [-4, -7, -6, -7, -4, 6], [1, 1, 0, 1, 2, -3], [6, -3, -8, -2, -3, 0], [-1, 1, 3, 1, 1, 0], [4, 4, 3, 4, 4, -3], [-7, -2, -1, -2, -7, 1], [1, 4, 3, -5, 4, 0], [1, -1, -6, -1, 1, 6], [-4, 0, 1, 0, -4, -1], [3, -6, 0, 3, -7, 0], [9, 0, 6, 6, 0, 0], [1, 3, 9, 3, 3, 0], [6, -4, 0, 6, -6, -8], [-3, 6, 9, -3, 6, 0], [-1, -2, 0, -1, 2, 4], [8, 3, 7, 3, 8, -7], [-1, -1, 0, -1, 3, 3], [0, 3, 0, 0, 3, -3], [-1, 3, 6, 3, -1, -6], [-3, 3, 0, -3, -1, 3], [4, -1, -3, -1, -1, 0], [-2, 6, 0, -2, 1, -2], [-6, 1, 7, 1, -6, -7], [3, -3, -3, 3, -3, 0], [0, -6, -3, 9, -6, 0], [-8, -5, -3, -5, -8, 3], [-5, 4, 0, -5, 0, 6], [-4, -1, -8, -6, -1, 0], [-3, 7, 12, -2, 7, 0], [-4, 8, 0, -4, -11, 0], [-9, -4, 0, -4, -9, 0], [-19, -1, 0, -1, -19, 0], [-4, 8, 0, -4, 15, 0], [-10, 8, 1, -15, 8, 0], [10, -8, 0, 10, -5, -12], [12, -1, 6, -1, 12, -6], [-14, 7, 3, -11, 7, 0], [-10, 14, 0, -10, 8, 6], [2, -10, -9, -10, 2, 9], [10, 1, -4, -6, 1, 0], [13, -2, -3, 1, -2, 0], [-11, 0, -3, 0, -11, 3], [23, -2, -1, -2, 23, 1], [2, -1, 0, 2, 0, -3], [1, -14, 0, 1, -8, 12], [0, -7, -9, 5, -7, 0], [10, -15, 0, 10, 1, -5], [-1, 9, 0, 9, -1, 0], [-9, -3, -3, -3, -9, 3], [1, -6, -9, -6, 1, 9], [9, -12, 0, 9, 6, -6], [-7, -1, 0, -7, -1, 15], [24, -2, 0, -2, 24, 0], [0, -9, -12, -9, 0, 12], [18, -9, -1, 17, -9, 0], [-6, -7, -3, -7, -6, 3], [4, 1, 0, 4, -16, -9], [20, -5, 12, 22, -5, 0], [-6, 7, 0, -6, 12, 5], [20, -6, -5, -6, 20, 5], [0, -6, -3, 9, -6, 0], [-2, -5, 0, -2, -17, 9], [2, 2, 0, 2, -8, -6], [-5, 10, 0, -5, -5, 0], [2, -4, 3, -4, 2, -3], [-22, 5, -6, -16, 5, 0], [25, -4, -6, 2, -4, 0], [5, 5, 6, 5, 5, -6], [-12, 8, 2, 8, -12, -2], [-18, -3, -7, -1, -3, 0], [4, -10, -9, -10, 4, 9], [13, -4, -11, -4, 13, 11], [-9, 24, 0, -9, 13, -6], [-14, 10, 17, -3, 10, 0], [-14, 0, 5, 0, -14, -5], [14, -3, -6, 0, -3, 0], [-2, 1, 0, -2, -26, 3], [0, 6, 0, 0, 16, -6], [-7, -4, -9, -1, -4, 0], [11, -10, 0, 11, 5, -12], [3, -12, -6, 18, -12, 0], [-10, -3, -6, 0, -3, 0], [5, 8, 6, -10, 8, 0], [-2, -5, -12, -5, -2, 12], [-10, 11, 2, -20, 11, 0], [-6, 25, 0, -6, 27, -13], [15, -6, 6, -6, 15, -6], [7, -14, 0, 7, 4, 0], [-1, -5, -18, -8, -5, 0], [3, 5, 11, 5, 3, -11], [3, -3, -15, -9, -3, 0], [2, -4, 0, 2, -4, 0], [-23, -3, -3, -3, -23, 3], [-6, 6, 0, -6, 9, 6], [-15, 6, 12, 0, 6, 0], [-4, 3, 0, -4, -19, 5], [0, 13, 0, 13, 0, 0], [-17, 2, 9, 5, 2, 0], [34, 3, 8, 3, 34, -8], [3, -18, 0, 3, -16, 12], [27, 3, 9, 3, 3, 0], [7, 1, 0, 7, 10, -15], [14, -8, 5, -8, 14, -5], [5, -10, 0, 5, 18, 0], [17, -5, -3, -5, 17, 3], [-21, 9, 6, 9, -21, -6], [4, -2, 18, 22, -2, 0], [-11, 3, 3, 3, -11, -3], [-14, -2, 2, 6, -2, 0], [-6, 2, 12, 2, -6, -12], [16, -11, -18, 4, -11, 0], [10, 11, 3, 11, 10, -3], [-10, 8, 0, -10, -13, 12], [8, -1, -6, -4, -1, 0], [-3, 15, 0, -3, -6, -9], [-5, 1, 0, -5, -23, 9], [18, -15, -21, 9, -15, 0], [14, -12, 0, 14, -16, -16], [-3, 12, 0, -3, -11, -6], [21, 0, 8, 8, 0, 0], [-12, 9, 0, -12, 24, 15], [1, -5, 0, 1, 10, 3], [-16, -1, -19, -17, -1, 0], [7, 15, 12, -18, 15, 0], [6, -4, -13, -4, 6, 13], [0, 0, 0, 0, 16, 0], [-10, 5, 24, 14, 5, 0], [-11, 3, 3, -3, 3, 0], [19, -6, 8, -6, 19, -8], [2, -2, 9, -2, 2, -9], [-20, 7, 0, 7, -20, 0], [0, 6, 0, 0, -25, -6], [24, 3, -7, -13, 3, 0], [1, 13, 0, 1, 26, -15], [-28, 2, -3, -7, 2, 0], [-14, -4, -15, -7, -4, 0], [7, -20, 0, 7, -11, 6], [9, -12, -24, -12, 9, 24], [-1, 17, 12, 17, -1, -12], [25, 6, 9, -3, 6, 0], [-25, -25, -18, -25, -25, 18], [-26, 5, -9, -19, 5, 0], [-12, 11, 0, -12, 24, 13], [-34, 9, 4, 9, -34, -4], [-10, 8, 16, 0, 8, 0], [5, -7, 0, 5, -20, -3], [-10, -7, -15, -1, -7, 0], [-8, 16, 0, -8, 13, 0], [-22, -7, -12, -7, -22, 12], [-23, -7, -15, -1, -7, 0], [38, -8, -12, -8, 38, 12]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_252_j_Hecke(Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_252_2_j_a();".
// This may take a long time!  To see verbose output, uncomment the SetVerbose lines below.
// The precision argument determines an initial guess on how many Fourier coefficients to use.
// This guess is increased enough to uniquely determine the newform.
function MakeNewformModFrm_252_2_j_a(:prec:=6)
    chi := MakeCharacter_252_j();
    f_vec := qexpCoeffs();
    Kf := Universe(f_vec);
    // SetVerbose("ModularForms", true);
    // SetVerbose("ModularSymbols", true);
    S := CuspidalSubspace(ModularForms(chi, 2));
    S := BaseChange(S, Kf);
    maxprec := NextPrime(997) - 1;
    while true do
        trunc_vec := Vector(Kf, [0] cat [f_vec[i]: i in [1..prec]]);
        B := Basis(S, prec + 1);
        S_basismat := Matrix([AbsEltseq(g): g in B]);
        if Rank(S_basismat) eq Min(NumberOfRows(S_basismat), NumberOfColumns(S_basismat)) then
            S_basismat := ChangeRing(S_basismat,Kf);
            f_lincom := Solution(S_basismat,trunc_vec);
            f := &+[f_lincom[i]*Basis(S)[i] : i in [1..#Basis(S)]];
            return f;
        end if;
        error if prec eq maxprec, "Unable to distinguish newform within newspace";
        prec := Min(Ceiling(1.25 * prec), maxprec);
    end while;
end function;


// To make the Hecke irreducible modular symbols subspace (type ModSym)
// containing the newform, type "MakeNewformModSym_252_2_j_a();".
// This may take a long time!  To see verbose output, uncomment the SetVerbose line below.
// The default sign is -1.  You can change this with the optional parameter "sign".
function MakeNewformModSym_252_2_j_a( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_252_j();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,2,sign)));
    Vf := Kernel([<5,R![1, 4, 17, -2, 5, 1, 1]>],Snew);
    return Vf;
end function;